WO2018006563A1 - Non-aqueous electrolyte solution for lithium-ion battery and lithium-ion battery - Google Patents

Abstract

A non-aqueous electrolyte solution for a lithium-ion battery and a lithium-ion battery. The non-aqueous electrolyte solution for a lithium-ion battery comprises an unsaturated phosphate compound and a sulfone compound. The sulfone compound comprises a cyclic sulfone compound and/or a straight-chain sulfone compound. The unsaturated phosphate compound has a structure as represented by formula I. The cyclic sulfone compound has a structure as represented by formula II. The straight-chain sulfone compound has a structure as represented by formula III. According to the non-aqueous electrolyte solution, an unsaturated phosphate compound and a sulfone compound are both added to the electrolyte solution, so as to form a protective film which is even in components, appropriate in thickness, and high in density on the electrode interface; the combination of the two compounds enables the electrolyte solution to have a higher stability at the positive electrode, and brings an excellent high temperature performance and cycling performance to the battery; moreover, the combination of the two compounds enables the battery to maintain low impedance, so as to obtain an excellent low temperature performance. The electrolyte solution lays the foundation for the preparation of high-quality power battery.

Description

Lithium ion battery non-aqueous electrolyte and lithium ion battery Technical field

The present application relates to the field of lithium ion battery electrolytes, and in particular to a lithium ion battery non-aqueous electrolyte and a lithium ion battery.

Background technique

Compared with other batteries, lithium-ion batteries have the advantages of light weight, small size, high operating voltage, high energy density, high output power, high charging efficiency, no memory effect and long cycle life. Used in the 3C consumer electronics market. And with the development of new energy vehicles, non-aqueous electrolyte lithium-ion batteries are becoming more and more popular as power supply systems for automobiles. With the continuous improvement of the cruising range requirements of new energy vehicles, the high energy density of power lithium-ion batteries is increasingly required. The ternary nickel-cobalt-manganese cathode material has become a research hotspot of new energy power battery cathode materials due to its high energy density, low cost, excellent performance and relatively good safety, and with the continuous energy density of power batteries. Improvement, ternary nickel-cobalt-manganese material power battery is moving toward high voltage.

However, the ternary nickel-cobalt-manganese material has the disadvantage of insufficient high-temperature performance as a positive electrode material. In the ternary nickel-cobalt-manganese material, the nickel element has a strong catalytic effect on the electrolyte, which catalyzes the decomposition of the electrolyte, thereby reducing the discharge capacity. And the accumulation of decomposition products leads to a significant increase in internal resistance; this condition becomes particularly severe under conditions of high voltage, high temperature and high nickel content, which greatly deteriorates battery performance and hinders high voltage ternary nickel cobalt manganese. Material batteries are put to practical use in the field of power batteries.

The electrolyte is a key factor affecting the overall performance of the battery. In particular, the additives in the electrolyte are particularly important for the performance of the battery. Therefore, in order to give full play to the performance of the power battery of the ternary nickel-cobalt-manganese material, the matching of the electrolyte is the key. The currently practical lithium ion battery electrolyte is a non-aqueous electrolyte added with a conventional film-forming additive such as vinylene carbonate (abbreviation VC) or fluoroethylene carbonate (abbreviated as FEC), and the battery is excellent by the addition of VC and FEC. Cyclic performance. However, the high voltage stability of VC is poor, and FEC is easy to decompose gas at high temperatures. Therefore, under high voltage and high temperature conditions, these additives are difficult to meet the performance requirements of high temperature cycle.

Patent application No. 201410534841.0 discloses a novel film-forming additive for a phosphate compound containing a triple bond, which not only improves high temperature cycle performance, but also significantly improves storage performance. Sulfone compounds have also been reported very early in the literature (Journal of Power Sources 179 (2008) 770–779), mainly to improve the stability of high-voltage batteries and improve cycle performance. However, in the research, the scientific and technological workers in the field found that the passivation film formed by the three-bond phosphate ester additive at the electrode interface is poor in conductivity, resulting in a large interface impedance, which significantly degrades the low temperature performance, and is particularly likely to cause the battery to be at a low temperature. Lithium-deposited lithium is used to suppress the application of non-aqueous lithium-ion batteries under low temperature conditions.

Summary of the invention

The purpose of the present application is to provide a new lithium ion battery non-aqueous electrolyte and a lithium ion battery.

In order to achieve the above objectives, the present application adopts the following technical solutions:

An aspect of the present application discloses a lithium ion battery non-aqueous electrolyte comprising unsaturated phosphate esters and a sulfone compound, and the sulfone compound includes a cyclic sulfone compound and/or a linear sulfone compound;

The unsaturated phosphate compound has the structure shown in Formula 1,

Wherein R1, R2, and R3 are each independently selected from a hydrocarbon group having 1-4 carbon atoms, and at least one of R1, R2, and R3 is an unsaturated hydrocarbon group having a double bond or a hydrazone bond;

The cyclic sulfone compound has a structure represented by Formula 2, and the linear sulfone compound has a structure represented by Formula 3,

Wherein R 4 , R 5 , R 6 and R 7 are each independently selected from a hydrogen atom, a halogen or an alkyl group having 1 to 5 carbon atoms, and A is a substituted or unsubstituted alkylene group having 2 to 6 carbon atoms. The functional group substituted may be a halogen or an alkyl group having 1 to 3 carbon atoms.

It should be noted that the key point of the present application is that the above unsaturated phosphate compound and sulfone compound are simultaneously added to the nonaqueous electrolyte of the lithium ion battery, and the interface impedance caused by the addition of the unsaturated phosphate compound alone is overcome. Defects such as lithium deposition at high and low temperatures. The sulfone compound may be a cyclic sulfone compound or a linear sulfone compound, or may be used in combination.

It should be noted that the application of the sulfone compound to the electrolyte solution is not proposed in the present application. The present application has been extensively studied and tested to find that the sulfone compound and the above unsaturated phosphate compound can be used together to obtain a better one. The present application is made by high and low temperature performance and cycle performance. It is to be understood that the present application is based on the patent application No. 201410534841 and the priority of the patent application No. 201510397735.7, the related technical content and terminology of the above two patent applications are applicable to the present application. In addition, the key to the present application is to use a sulfone compound in combination with the above unsaturated phosphate compound. As the specific sulfone compound and the above unsaturated phosphate compound, conventional or uncommon compounds in the laboratory can be used. However, in order to ensure the performance of the non-aqueous electrolyte, in the preferred embodiment of the present application, specific types and even specific compounds of the sulfone compound and the above unsaturated phosphate compound are described and defined, which will be described later. Detailed in the program.

Preferably, the unsaturated phosphate compound of the present application is at least one selected from the group consisting of the compounds of the structural formula shown in Table 1, that is, the unsaturated phosphate compound is at least one selected from the group consisting of Compound 1 to Compound 6.

Table 1 Unsaturated phosphate ester compounds for non-aqueous electrolytes of lithium ion batteries

It can be understood that the unsaturated phosphate compound shown in Formula 1, or the unsaturated phosphate compound of Compound 1 to Compound 6, is a preferred technical solution of the present application, and does not exclude other compounds having similar physical and chemical properties. Saturated phosphate compounds.

More preferably, the cyclic sulfone compound is at least one of the structural compounds represented by Formula 4 and/or Formula 5,

Wherein R8 to R16 are each independently selected from a hydrogen atom, a halogen or an alkyl group having 1 to 5 carbon atoms.

More preferably, the sulfone compound is selected from the group consisting of sulfolane, 3-methylsulfolane, 3,3,4,4-tetrafluorosulfolane, cyclopentanesulfone, dimethylsulfone, methylethylsulfone and diethylsulfone. At least one.

It can be understood that the sulfone compound represented by the formula II to formula V, or the specifically defined sulfone compound, is a preferred technical solution of the present application, and other sulfone compounds having similar physical and chemical properties are not excluded.

Preferably, in the non-aqueous electrolyte of the lithium ion battery of the present application, the unsaturated phosphate compound occupies the non-aqueous battery of the lithium ion battery. 0.1% to 2% of the total weight of the electrolyte.

Preferably, in the nonaqueous electrolyte of the lithium ion battery of the present application, the unsaturated phosphate compound accounts for 0.2% to 1% of the total weight of the nonaqueous electrolyte of the lithium ion battery.

Preferably, in the nonaqueous electrolyte of the lithium ion battery of the present application, the sulfone compound accounts for 0.1% to 30% of the total weight of the nonaqueous electrolyte of the lithium ion battery.

Preferably, the sulfone compound accounts for 0.1% to 10% of the total weight of the nonaqueous electrolyte of the lithium ion battery.

Further preferably, the sulfone compound accounts for 0.5 to 10% by weight based on the total weight of the lithium ion battery nonaqueous electrolyte.

More preferably, the sulfone compound accounts for 1 to 10% of the total weight of the nonaqueous electrolyte of the lithium ion battery.

In the non-aqueous electrolyte of the lithium ion battery of the present application, when the amount of the unsaturated phosphate compound is less than 0.1%, the film forming effect of the positive and negative electrodes is poor, and the effect of improving the performance is not obtained; and when the amount thereof is too high, When it is more than 2%, the film thickness at the electrode interface is increased, the battery resistance is increased, and the battery performance is deteriorated.

Meanwhile, when the content of the sulfone compound is less than 0.1%, the sulfone compound cannot function effectively; when the content of the sulfone compound is more than 10%, in fact, within a certain range, for example, 30% or less, the comparison can still be exhibited. Good performance. When the content of the sulfone compound is more than 30%, the viscosity of the electrolyte is excessively large, and the film formation at the electrode interface is thick, the battery impedance is increased, and the battery performance is deteriorated.

It should be noted that the key of the present application is to use an unsaturated phosphate compound in combination with a sulfone compound to improve high and low temperature performance and cycle performance; it can be understood that the change in the amount of the two will inevitably directly affect the performance of the electrolyte. Thereby affecting the high and low temperature performance and cycle performance of the battery. Therefore, in the preferred embodiment of the present application, the amount of both is particularly limited in order to secure the performance of the electrolyte and the battery. It can be understood that, within the scope defined by the present application, the configured non-aqueous electrolyte has good high-low temperature performance and cycle performance; if it exceeds the range, its corresponding performance is inevitably affected, but for some requirements relatively Low or lower usage requirements can also improve the high and low temperature performance or cycle performance of the battery to some extent.

Further, in the nonaqueous electrolyte of the lithium ion battery of the present application, the weight ratio of the sulfone compound to the unsaturated phosphate compound is greater than or equal to 0.2. When the content of the unsaturated phosphate compound is high and the content of the sulfone compound is low, the low temperature performance is remarkably insufficient.

Preferably, in the non-aqueous electrolyte of the present application, the organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate. At least one.

Preferably, in the nonaqueous electrolyte of the present application, the lithium salt is selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide and difluorosulfonate. At least one of the lithium imide salts.

The other side of the application discloses a lithium ion battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution, wherein the electrolyte solution is the lithium ion battery non-aqueous electrolyte solution of the present application.

The charge cutoff voltage of the lithium ion battery of the present application is greater than or equal to 4.35V.

Preferably, in the lithium ion battery of the present application, the positive electrode is selected from the group consisting of LiCoO2, LiNiO2, LiMn2O4, LiCo1-yMyO2, At least one of LiNi1-yMyO2, LiMn2-yMyO4, and LiNixCoyMnzM1-xy-zO2; wherein, M is selected from the group consisting of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr At least one of V and Ti, and 0 ≤ y ≤ 1, 0 ≤ x ≤ 1, 0 ≤ z ≤ 1, x + y + z ≤ 1.

It should be noted that the non-aqueous electrolyte of the present application has been developed for a lithium ion battery, and thus can be applied to various lithium ion batteries including, but not limited to, the types listed in the present application.

Due to the adoption of the above technical solutions, the beneficial effects of the present application are:

In the non-aqueous electrolyte of the present application, the unsaturated phosphate compound and the sulfone compound are combined and added to the electrolyte to form a protective film having a uniform composition, a moderate thickness, and a good density at the electrode interface; The use of the electrolyte can make the electrolyte have good stability on the positive electrode, so that the battery obtains excellent high temperature performance and cycle performance, and can maintain the battery with low impedance and excellent low temperature performance of the battery. The non-aqueous electrolyte of the present application lays a foundation for preparing a high-quality power battery.

detailed description

The key point of the present application is that the unsaturated phosphate compound represented by Formula 1 and the sulfone compound are combined and added to the non-aqueous electrolyte to keep the battery low while not affecting high temperature performance and cycle performance. The internal resistance, in turn, gives the battery excellent low temperature performance.

Among them, the unsaturated phosphate compound represented by Formula 1 can form a stable passivation film on the surface of the negative electrode, and can prevent the reductive decomposition of the electrolyte to a large extent. In addition, the unsaturated phosphate compound can also form a protective film on the surface of the positive electrode, which can further prevent the electrolyte from being oxidatively decomposed on the surface of the positive electrode and suppress the elution of the positive metal ion, especially when the charging voltage is equal to or greater than 4.35V. The effect is more obvious, and the high-temperature performance and cycle performance of the lithium battery can be significantly improved, but the addition of the unsaturated-phosphate compound also causes an increase in internal resistance, thereby deteriorating the low-temperature performance.

In view of the above problems, the present application adds a sulfone compound to the unsaturated phosphate compound shown in Formula One. Since the oxidation potential of the sulfone compound is low, a protective film having a small thickness, a uniform composition, and a good density can be formed on the positive electrode. The denseness of the protective film can effectively improve the decomposition reaction of the electrolyte in the positive electrode, prevent the dissolution of the positive electrode metal ions; the thickness of the protective film and the uniformity of the composition can effectively reduce the impedance; and the reduction of the impedance can make the battery obtain an excellent low temperature. performance.

Therefore, the beneficial effects of the lithium ion battery non-aqueous electrolyte of the present application are as follows:

(1) The unsaturated phosphate ester compound can form a uniform dense passivation film on the positive electrode, so that the electrolyte has good stability, so that the battery has excellent high temperature performance and cycle performance. The sulfone compound can also be formed on the electrode, and the resulting film composition is uniform and dense, so that the battery has a lower impedance, so that the battery has excellent low temperature performance.

(2) The unsaturated phosphate compound and the sulfone compound shown in Formula 1 are combined and added to the electrolyte to form a protective film with uniform composition, moderate thickness and good compactness at the electrode interface; Use, you can get the battery Excellent high temperature performance and cycle performance, and the combination of the two can keep the battery low impedance, so that the battery can obtain excellent low temperature performance.

Further, in order to secure the performance of the nonaqueous electrolyte, the amount of the monounsaturated phosphate compound and the sulfone compound is limited in the present application. Wherein, the sulfone compound accounts for 0.5% to 30% of the total weight of the nonaqueous electrolyte of the lithium ion battery, preferably 1 to 10% of the total weight of the nonaqueous electrolyte of the lithium ion battery, which is to obtain more in the electrolyte. High chemical stability and full performance of the electrolyte. Moreover, in a preferred implementation of the present application, a cyclic sulfone compound and a chain sulfone compound are simultaneously added, and the two synergistically react, and the content of the cyclic sulfone compound is 1-3 of the total weight of the electrolyte. %, the content of the chain sulfone compound is 1-2% of the total weight of the electrolyte, and the synergistic effect of the two is that the thickness of the protective film formed on the positive electrode is relatively uniform, and the compactness is good, the impedance can be effectively reduced, and the performance of the battery is improved. .

The present application will be further described in detail below by way of specific embodiments and the accompanying drawings. The following examples are only intended to further illustrate the present application and are not to be construed as limiting the invention.

Example 1

The preparation method of the lithium ion battery of the present invention comprises a positive electrode preparation step, a negative electrode preparation step, an electrolyte preparation step, a separator preparation step, and a battery assembly step. details as follows:

The positive electrode preparation step is: mixing the positive active material LiNi0.5Co0.2Mn0.3O2, the conductive carbon black and the binder polyvinylidene fluoride according to the mass ratio of 96.8:2.0:1.2, and dispersing in N-methyl-2-pyrrolidone The positive electrode slurry is obtained, and the positive electrode slurry is uniformly coated on both sides of the aluminum foil, dried, calendered and vacuum dried, and the aluminum lead wire is welded by an ultrasonic welding machine to obtain a positive electrode plate, and the thickness of the electrode plate is 120- Between 150μm.

The preparation step of the negative electrode is: mixing graphite, conductive carbon black, binder styrene butadiene rubber and carboxymethyl cellulose in a mass ratio of 96:1:1.2:1.8, dispersing in deionized water to obtain a negative electrode slurry, and the negative electrode slurry The material is coated on both sides of the copper foil, dried, calendered and vacuum dried, and the nickel lead wire is welded by an ultrasonic welder to obtain a negative electrode plate having a thickness of 120-150 μm.

The electrolyte preparation step is: mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of EC:EMC:DEC=3:3:4, and adding lithium hexafluorophosphate at a concentration of 1.0 mol/L after mixing. 0.1 wt% of tripropargyl phosphate and 0.5 wt% of sulfolane were added based on the total weight of the electrolyte.

The separator preparation step is as follows: a three-layer separator of polypropylene, polyethylene and polypropylene is used, and the thickness is 20 μm.

The battery assembly step is: placing a three-layer separator having a thickness of 20 μm between the positive electrode plate and the negative electrode plate, and then winding the sandwich structure composed of the positive electrode plate, the negative electrode plate and the separator, and then squashing the wound body and placing it In the square aluminum metal shell, the lead wires of the positive and negative electrodes are respectively welded to the corresponding positions of the cover plate, and the cover plate and the metal shell are welded together by a laser welding machine to obtain the battery core to be injected; The electrolyte is injected into the cell through the injection hole, and the amount of the electrolyte is required to fill the gap in the cell.

Then follow the steps below to carry out the normalization of the first charge: 0.05C constant current charging for 3min, 0.2C constant current charging for 5min, 0.5C constant current charging for 25min, shelving for 1h, shaping, refilling, sealing, and then further with a current of 0.2C The constant current is charged to 4.2V, and after being kept at normal temperature for 24 hours, the constant current is constantly charged to 4.2V at 0.2C, and then discharged to 3.0V with a constant current of 0.2C. Obtain the lithium ion battery of this example.

The lithium ion battery prepared in this example was tested as follows:

(1) High-temperature cycle performance test: At 45 ° C, the formed battery was charged to 4.35 V with a constant current of 1 C, and then discharged to 3.0 V with a constant current of 1 C. After charging/discharging 300 cycles, the retention rate of the 300th cycle capacity was calculated to evaluate the high temperature cycle performance. Calculated as follows:

The 300th cycle capacity retention ratio (%) = (300th cycle discharge capacity / first cycle discharge capacity) × 100%.

(2) Normal temperature cycle performance test: At 25 ° C, the formed battery was charged to 4.35 V with a constant current of 1 C, and then discharged to 3.0 V with a constant current of 1 C. The retention rate of the 500th cycle capacity was calculated after 500 cycles of charging/discharging to evaluate the normal temperature cycle performance. Calculated as follows:

500th cycle capacity retention rate (%) = (500th cycle discharge capacity / first cycle discharge capacity) × 100%;

(3) High-temperature storage performance: The battery after the formation is charged to 4.35V at a normal temperature with a constant current of 1C, and the initial discharge capacity of the battery is measured, and then stored at 60 ° C for 30 days, discharged at 1 C to 3.0 V, and the battery is measured. Maintain capacity and recover capacity. Calculated as follows:

Battery capacity retention rate (%) = retention capacity / initial capacity × 100%;

Battery capacity recovery rate (%) = recovery capacity / initial capacity × 100%.

(4) Low-temperature discharge performance test: The battery after the formation was charged to 4.35 V with a constant current of 1 C at 25 ° C, and then discharged to 3.0 V with a constant current of 1 C, and the discharge capacity was recorded. Then, 1C constant current and constant voltage were filled, and after being placed in an environment of -20 ° C for 12 hours, the 1C constant current was discharged to 3.0 V, and the discharge capacity was recorded.

The low temperature discharge efficiency value of -20 ° C = 1 C discharge capacity (-20 ° C) / 1 C discharge capacity (25 ° C).

(5) Normal low temperature DC impedance (DCIR) performance test: At 25 ° C, the battery 1C after the formation is charged to a semi-electric state, and charged and discharged with 0.1C, 0.2C, 0.5C, 1C and 2C for ten seconds respectively. Record the charge and discharge cutoff voltage. Then, the charge and discharge currents at different magnifications are plotted on the abscissa (unit: A), and the cutoff voltage corresponding to the charge and discharge current is plotted on the ordinate, and a linear relationship diagram (unit: mV) is made.

Charge DCIR value = slope value of a linear plot of different charge currents and corresponding cutoff voltages.

Discharge DCIR value = slope value of a linear plot of different discharge currents and corresponding cutoff voltages.

(6) In addition, after the formed battery was charged at 0.3 C at 0 ° C, the degree of lithium deposition of the negative electrode was measured and evaluated by a 5-point system. The lower the fraction, the more severe the lithium deposition. Specifically, 5 points means no lithium, 4 means less lithium, 3 means general lithium, 2 means more serious lithium, and 1 means severe lithium.

All test results of this example are shown in Table 3.

Example 2-20

In Examples 2 to 20, the same procedures as in Example 1 were carried out except for the specific compounds of the sulfone compound and the unsaturated phosphate compound, and the amounts thereof. The specific compounds of the respective examples, and the amounts thereof are shown in Table 2, wherein the amounts are calculated as a percentage of the total weight of each of the nonionic electrolytes of the lithium ion battery.

In addition, the present application also designed six comparative examples, namely, Comparative Examples 1-6. Similarly, the six comparative examples are only different from the specific compounds and amounts added in the first embodiment or other examples, and the others are different. The same as in the first embodiment. The specific compounds of the respective comparative examples, and the amounts thereof are shown in Table 2, and the amounts thereof are calculated as a percentage of the added matter to the total weight of the nonaqueous electrolyte of the lithium ion battery.

Table 2 Materials and amounts of each of the examples and comparative examples

Example	Tripropargyl phosphate	Diallylethyl phosphate	Sulfolane	Methyl ethyl sulfone	Dimethyl sulfone	VC
Example 1	0.1		0.5
Example 2	0.5		1
Example 3	1		5
Example 4	1		10
Example 5	1		30
Example 6	2		10
Example 7	0.5		10
Example 8	1			5
Example 9	1			10
Example 10	1				5
Example 11	1				10
Example 12	1		5	5
Example 13	1		5		5
Example 14		0.1	0.5
Example 15		0.5	1
Example 16		1	5
Example 17		1	10
Example 18		1	30

Example 19		2	10
Example 20	2		0.3
Comparative example 1	1
Comparative example 2			5
Comparative example 3				5
Comparative example 4					5
Comparative example 5						1
Comparative example 6		1

In the table, the blank indicates that the corresponding substance or the comparative example was not added, and the tripropargyl phosphate was the compound 1 in Table 1, and the diallylethyl phosphate was the compound 4 in Table 1.

The test results of Examples 1-20 and Comparative Examples 1-6 are shown in Table 3.

Table 3 Test results of each example and comparative example

In Table 2, 0 ° C 0.3 C charging, negative electrode lithium degree test, 5 means no lithium, 4 means a little lithium, 3 means general lithium, 2 means more serious lithium, 1 means severe lithium.

By comparing the test results of Comparative Examples 1-6, it can be found that when the unsaturated phosphate compound is used alone, the cycle performance and high temperature storage are better, and the low temperature performance is poor. When the sulfone compound is used alone, the cycle performance and high-temperature storage performance are poor, and the low-temperature performance is good.

In the test results of Examples 1-20 of the present application, by comparing Comparative Example 1 with Examples 3-5 and 8-13, it can be found that the addition of a sulfone compound based on the unsaturated phosphate compound is not only The low temperature performance can be significantly improved, and the cycle performance and high temperature performance are also significantly improved.

Meanwhile, in the test results of Examples 1 to 20 of the present application, it was found that with respect to Comparative Examples 1 to 6, it was found that all of the examples including the unsaturated phosphate compound and the sulfone compound have high temperature properties and low temperature properties. improve. By comparison of Examples 4, 6, and 7, and 17 and 19, as the unsaturated phosphate ester compound increases, its high temperature performance is improved, but the low temperature performance is relatively decreased, especially the impedance, and the amount of the impedance increases. It also increases. Especially when the content of the unsaturated phosphate compound is high and the content of the sulfone compound is low, the low temperature performance is remarkably insufficient.

In summary, the present application combines an unsaturated phosphate compound and a sulfone compound, and at a suitable ratio, the battery can obtain excellent high temperature performance and cycle performance as well as good low temperature performance. Among them, in terms of dosage, not enough The amount of the phosphate ester is 0.1% to 2%, and the amount of the sulfone compound is 0.1% to 30%, which can improve the high-temperature performance and the cycle performance; and the amount of the unsaturated phosphate is 0.2% to 1%, and the sulfone compound When the dosage is 1 to 10%, the effect is better.

The above content is a further detailed description of the present application in conjunction with the specific embodiments, and the specific implementation of the present application is not limited to the description. It will be apparent to those skilled in the art that the present invention can be made in the form of the present invention without departing from the scope of the present invention.

Claims (9)

1. A nonaqueous electrolyte for a lithium ion battery, comprising: an unsaturated phosphate compound and a sulfone compound, wherein the sulfone compound comprises a cyclic sulfone compound and/or a linear sulfone compound;

   The unsaturated phosphate compound has the structure shown in Formula 1,

   

   Wherein R1, R2, and R3 are each independently selected from a hydrocarbon group having 1-4 carbon atoms, and at least one of R1, R2, and R3 is an unsaturated hydrocarbon group having a double bond or a hydrazone bond;

   The cyclic sulfone compound has a structure represented by Formula 2, and the linear sulfone compound has a structure represented by Formula 3,

   

   Wherein R 4 , R 5 , R 6 and R 7 are each independently selected from a hydrogen atom, a halogen or an alkyl group having 1 to 5 carbon atoms, and A is a substituted or unsubstituted alkylene group having 2 to 6 carbon atoms. The functional group substituted is a halogen or an alkyl group having 1 to 3 carbon atoms.
2. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the cyclic sulfone compound is at least one of the structural compounds represented by the formula IV and/or the formula 5.

   

   Wherein R8 to R16 are each independently selected from a hydrogen atom, a halogen or an alkyl group having 1 to 5 carbon atoms.
3. The nonaqueous electrolyte for a lithium ion battery according to claim 1, wherein the sulfone compound is selected from the group consisting of sulfolane, 3-methylsulfolane, 3,3,4,4-tetrafluorosulfolane, and cyclopentane. At least one of dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
4. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 3, wherein the unsaturated phosphate compound accounts for 0.1% to 2% of the total weight of the nonaqueous electrolyte of the lithium ion battery, preferably Lithium The ion battery has a total weight of 0.2% to 1% of the non-aqueous electrolyte.
5. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 3, wherein the sulfone compound accounts for 0.1% to 30% by weight of the total weight of the nonaqueous electrolyte of the lithium ion battery, preferably, 0.1 to 10% of the total weight of the nonaqueous electrolyte of the lithium ion battery, further preferably 0.5 to 10% of the total weight of the nonaqueous electrolyte of the lithium ion battery, more preferably, the total weight of the nonaqueous electrolyte of the lithium ion battery 1 to 10%.
6. The nonaqueous electrolyte for a lithium ion battery according to any one of claims 1 to 3, wherein a weight ratio of the sulfone compound to the unsaturated phosphate compound is greater than or equal to 0.2.
7. A lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte solution is a lithium ion battery according to any one of claims 1 to 6 Electrolyte.
8. The lithium ion battery according to claim 7, wherein the positive electrode is one or two selected from the group consisting of LiCoO2, LiNiO2, LiMn2O4, LiCo1-yMyO2, LiNi1-yMyO2, LiMn2-yMyO4, and LiNixCoyMnzM1-xy-zO2. Above, wherein M is one or more selected from the group consisting of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0 ≤ y ≤ 1, 0 ≤ x ≤ 1, 0 ≤ z ≤ 1, x + y + z ≤ 1.
9. The lithium ion battery according to claim 7, wherein the lithium ion battery has a charge cutoff voltage greater than or equal to 4.35V.